One form of oval-shaped catalytic converter that is presently being manufactured and is used for treating the exhaust gas emitted by internal combustion engines includes an outer metallic housing which has a catalyst coated substrate located within the cavity of the housing. The substrate is wrapped with a mat of intumescent material which serves to support the substrate as well as provides an insulating barrier between the substrate and the housing. In addition, each end of the converter is provided with inner and outer cones which serve to reduce the (1) temperature of the outer end cone, (2) temperature of the mat retention material, and (3) transmission of noise through the end cone. In this type of converter, the mat material is used as the prime insulator and is used between the inner and outer end cones and between the substrate and the housing.
In an effort to simplify the manufacture and reduce the number of parts that are required, but not lose the advantages provided by catalytic converters of the type described above, it has been proposed in copending patent application U.S. Ser. No. 08/932,713, entitled "Catalytic Converter and Method of Manufacture," to eliminate the inner cone of the converter. By so doing, however, one finds that the mat is exposed directly to the hot exhaust gases. In order to allow the converter to be placed close to the engine where inlet exhaust gases reach as high as 950.degree. C. without the hot gases causing the mat to erode and lose its substrate retention and heat insulating capability, the above-mentioned copending patent application discloses an catalytic converter construction and a method of making the converter that provides the mat with increased density along the minor axis. This change in mat density results in the mat being able to withstand the high temperatures caused by the hot exhaust gases much longer without deteriorating and losing its ability to serve as an insulator and as a support for the substrate within the housing.
This invention is directed to another form of catalytic converter of the above-described type that dispenses with the inner cone but is intended to provide the same advantages realized by the converters utilizing dual end cone construction. The intent here is to use integral portions of the substrate body and the end member to shield the mat from the direct impingement of the exhaust gases.